Electron transfer mechanism
Anaerobes have potential to reduce organic compounds to support metabolism without oxygen but exoelectrogens have tendency to transfer electrons directly to chemicals that are not intermediate electron acceptors. Anaerobes transfer electrons to soluble compounds like nitrate and sulfate which can diffuse through cell membrane to cell, but exoelectrogens like Shewanella and Geobacter species are capable to transfer electrons outside of the cell [11]. Biofilm technologies are extensively being exploited for biotransformation, energy recovery, bioremediation and waste water treatment [12]. Biofilms are formed at cathode or anode either by inoculating the culture (for biosynthesis or bioremediation) or by natural microbial
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These electro active compounds also act as inhibitors and toxins for competitors [21]. Lactobacillus and Enterococcus species also release mediators the electro active compounds. Electron shuttle is an adaptive strategy under controlled conditions. Synthesis of mediators in the cell is an energetically expensive so it must recycled in the system. In microbial fuel cell with fed batch system these mediators are increased over time without the replacement of medium. But in continuous flow system these active electron shuttles does not play prominent role like in waste treatment because replacement of medium continuously flushed out these mediators from system and reduce the fuel cell efficiency nearly 50% [22]. Another factor limiting the current generation in the MFC is that microbes with natural mediators incompletely oxidize organic acids like lactate and pyruvate to acetate even the electrodes are acting as electron acceptors like Shewanella species. Similarly contaminants can consume the lactate so less electrons are recovered as electricity …show more content…
Mtr pathway is the main route for the reduction of electron acceptors or electrodes. It requires five proteins OmcA, MtrB, MtrC, MtrA and CymA. All these proteins reform C-type Cytochrome family. CymA proteins are present in the inner membrane of the cell and OmcA, MtrC are present on the outer membrane for the electron transport from inner side to outer electrodes. MtrA protein links the intra and extra cellular environment and OmcA proteins are for the attachment of biofilm to the electrode figure 4 [3]. The pili monofilaments are also known as microbial nanowires. These nanowires have resemblance to synthetic organic metals and exhibit metals like conductivity. These pilli or nanowires were first examined under scanning tunneling microscopy (STM). These appendages were conductive in the cell and surface so are able to carry electrons from cell to the surface [24]. Nanowires produced by G.sulsurreducens and Shewanella oneidensis are quite different. In G.sulsurreducens these nanowires are quite thin where as in Shewanella oneidensis these are like thick cables may be the bundle of several conductive wires. Some Photosynthetic microbes have potential for the production of nanowires like oxygenic Cyanobacteria. They can produce electricity in MFC in light but not in dark. It was studied that Shewanella oneidensis are conductive at micrometer scale and
In this experiment the heat shock method will be used to deliver a vector (plasmid) of GFP to transform and grow E. coli bacteria. Four plates containing Luria Bertani (LB) broth and either –pGLO and +pGLO will have E. coli bacteria added to it. The plate containing –pGLO (no pGLO) and LB will show growth as ampicillin will be present killing bacteria but no glowing because no arabinose will be present for glowing to be activated, the same result will be seen in the plate containing +pGLO, LB and ampicillin. The plate with –pGLO, LB and ampicillin will show no growth and no glowing as no arabinose is present for glowing to be activated
The diazonium salt is formed by the reaction of nitrous acid with the amine in acid solution. Nitrous acid is not stable and must be prepared in situ; in strong acid it dissociates to form nitroso ions, +NO, which attack the nitrogen of the amine. The intermediate so formed loses a proton, rearranges, and finally loses water to form the resonance-stabilized diazonium ion.
In 1935, Robert Robinson and his colleague William Sage Rapson published a series of articles for the Journal of the Chemical Society. In them, Robinson and Rapson detail how they performed a number of experiments that synthesized molecules similar in structure to sterols. In particular, Part 7 of their experiments describes what is today known in organic chemistry circles and classrooms alike as the Robinson Annulation Reaction. Figures 1 and 2 above demonstrate two examples of the mechanism for the Robinson Annulation Reaction. In Robinson’s words (1935), this reaction involves a ketone that “might undergo double cyclisation” with formation of a new structure (p. 1533). The Robinson Annulation Reaction constructs a new ring (for example, a six-membered ring) from the original starting ketone found in the reactants. Typically, a structure known as an enolate (the anion formed when an alpha hydrogen in the molecule of an aldehyde or a ketone is removed as a hydrogen ion and contains a double bond because it is resonance stabilized—source: science.uvu.edu) would be added to a methyl vinyl ketone or other enone (compound containing a ketone and an alkene). This process is also known as a base-catalyzed Michael addition. Dehydration, or removal of H2O, then occurs to give a cyclohexenone product.
Fuel cells could create new markets for steel, electronics, electrical and control industries and other equipment suppliers. They could provide tens of thousands of high-quality jobs and reduce trade deficits.
Greta Christina eloquently puts into words something I know in theory, but can be hard to understand in practice in heterosexual relationships. In Are we having sex now or what? Christina details her record keeping of how many people she had sex with, and what she counted as sex. She talks about the limiting misconception of sex only being coitus, and other acts not “counting.” Christina writes of how when she started having sex with women her outdated system of what was sex and what was not sex was completely destroyed. By limiting sex to “penis in vagina,” Christina was discounting some of her favorite sexual experiances, and including ones she did not particularly enjoy.
Talaro , K., & Chess, B. (2012). Foundations in microbiology. (8th ed., pp. 563-564). New York, NY:
Abstract: Enzymes are catalysts therefore we can state that they work to start a reaction or speed it up. The chemical transformed due to the enzyme (catalase) is known as the substrate. In this lab the chemical used was hydrogen peroxide because it can be broken down by catalase. The substrate in this lab would be hydrogen peroxide and the enzymes used will be catalase which is found in both potatoes and liver. This substrate will fill the active sites on the enzyme and the reaction will vary based on the concentration of both and the different factors in the experiment. Students placed either liver or potatoes in test tubes with the substrate and observed them at different temperatures as well as with different concentrations of the substrate. Upon reviewing observations, it can be concluded that liver contains the greater amount of catalase as its rates of reaction were greater than that of the potato.
Multiplication of attached organisms leads to confluent growth and biofilm formation. Adherent bacteria synthesise extracellular polymers.
Bacterial cells, like plant cells, are surrounded by a cell wall. However, bacterial cell walls are made up of polysaccharide chains linked to amino acids, while plant cell walls are made up of cellulose, which contains no amino acids. Many bacteria secrete a slimy capsule around the outside of the cell wall. The capsule provides additional protection for the cell. Many of the bacteria that cause diseases in animals are surrounded by a capsule. The capsule prevents the white blood cells and antibodies from destroying the invading bacterium. Inside the capsule and the cell wall is the cell membrane. In aerobic bacteria, the reactions of cellular respiration take place on fingerlike infoldings of the cell membrane. Ribosomes are scattered throughout the cytoplasm, and the DNA is generally found in the center of the cell. Many bacilli and spirilla have flagella, which are used for locomotion in water. A few types of bacteria that lack flagella move by gliding on a surface. However, the mechanism of this gliding motion is unknown. Most bacteria are aerobic, they require free oxygen to carry on cellular respiration. Some bacteria, called facultatibe anaerobes can live in either the presence or absence of free oxygen. They obtain energy either by aerobic respiration when oxygen is present or by fermentation when oxygen is absent. Still other bacteria cannot live in the presence of oxygen. These are called obligate anaerobes. Such bacteria obtain energy only fermentation. Through fermentation, different groups of bacteria produce a wide variety of organic compounds. Besides ethyl alcohol and lactic acid, bacterial fermentation can produce acetic acid, acetone, butyl alcohol, glycol, butyric acid, propionic acid, and methane, the main component of natural gas. Most bacteria are heterotrophic bacteria are either saprophytes or parasites. Saprophytes feed on the remains of dead plants and animals, and ordinarily do not cause disease. They release digestive enzymes onto the organic matter. The enzymes breakdown the large food molecules into smaller molecules, which are absorbed by the bacterial cells. Parasites live on or in living organisms, and may cause disease. A few types of bacteria are Autotrophic, they can synthesize the organic nutrients they require from inorganic substances. Autotrophic bacteria are either photosynthetic or Chemosynthetic. The photosynthetic bacteria contain chlorophyll that are different from the plant chlorophyll. In bacterial photosynthesis, hydrogen is obtained by the splitting of compounds other than water.
There are several types of treatment methods present but biological treatment methods have gained much traction in the recent years due to their low operation costs, comparatively benign effects on the environment and their ease of handling and maintenance. Biological wastewater treatment methods can be subcategorized into dispersed growth systems and attached growth systems. Biofilms fall under the latter category (Sehar & Naz, 2016)
Addition of air and mechanical mixing to enchance the growth of bacteria and ficilitate subsequent waste reduction
Biofilms are formed by a six step process. First is a reversible process, when an organic monolayer(made of polysaccharides or glycoproteins) absorbs to the surface, altering the chemical and physical properties of the surface. This makes the surface more conditioned and increase the chance that planktonic bacteria will attach. Secondly, also a reversible step, is when the free-floating or planktonic bacteria encounter the conditioned surface, and some attachment of the bacteria may occur. The third step is when the bacteria is left attached too long, then an irreversible attachment occurs. F...
There are many types of fuel cells, but they all consist of an anode, a cathode, and an electrolyte that allows positively charged hydrogen ions (or protons) to move between
The energy extracted today by the burning of coal and petroleum products represents sunlight energy captured and stored by photosynthesis almost 200 million years ago. A third very interesting group of bacteria synthesize sugars, not by using sunlight’s energy, but by extracting energy from inorganic chemical compounds; In a (d) deep sea vent, chemoautotrophs, such as these (e) thermophilic bacteria, capture energy from inorganic compounds to produce organic compounds.
[e-book] RAPS Consulting & Nano Energy,prepared for SECCP, Earthlife Africa Johannesburg. Available from: http://projects.gibb.co.za/Portals/3/projects/201002%20Nuclear%201/Appendix%20D%20Public%20Participation/App%20D8/potential%20of%20RE%20in%20SA%20Feb06.pdf [Accessed 7 April 2014]